One vertex per element, one color per generator, with an edge from x to x·s.
(5,6)(7,15,18,11)(8,19)(9,22)(10,13)(12,21)(14,25)(16,32,33,36)(17,27,23,29)(20,30)(24,28)(26,34,31,35)(37,38,42,48,43,47,41,46)(39,49,52,44,53,60,51,59)(40,54,55,62,56,45,57,61)(50,64,65,58,66,63,67,68)(1,2)(3,4)(5,7)(6,11)(8,16)(9,23)(10,18)(12,26)(13,15)(14,29)(17,25)(19,32)(20,33)(21,35)(22,27)(24,34)(28,31)(30,36)(37,39,43,53)(38,44,47,59)(40,50,56,66)(41,52,42,51)(45,58,54,68)(46,60,48,49)(55,67,57,65)(61,64,62,63)(2,4)(5,8,10,20)(6,12,13,28)(7,16,18,33)(9,24,25,21)(11,26,15,31)(14,30,22,19)(17,35,23,34)(27,32,29,36)(37,40)(38,45)(39,50)(41,55)(42,57)(43,56)(44,58)(46,61)(47,54)(48,62)(49,63)(51,65)(52,67)(53,66)(59,68)(60,64)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.